https://github.com/ntd/ardecoder
Decoding up to 3 incremental encoders with Arduino Uno or Nano
https://github.com/ntd/ardecoder
arduino encoder incremental-encoder nano quadrature rotary-encoder uno
Last synced: 17 days ago
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Decoding up to 3 incremental encoders with Arduino Uno or Nano
- Host: GitHub
- URL: https://github.com/ntd/ardecoder
- Owner: ntd
- License: mit
- Created: 2020-01-13T19:13:46.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2023-07-12T08:22:10.000Z (almost 2 years ago)
- Last Synced: 2025-02-15T23:42:03.053Z (2 months ago)
- Topics: arduino, encoder, incremental-encoder, nano, quadrature, rotary-encoder, uno
- Language: C++
- Homepage:
- Size: 131 KB
- Stars: 3
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
Ardecoder: decoding up to 3 encoder with Arduino Uno or Nano.
INSTALLATION
------------
It is assumed everything needed to build a project for your board (most
notably arduino, arduino-cli and board support) is already properly
installed on your system.
Ensure the Arduino board is connected to the PC and then:
```
# For new Arduino NANO:
make upload
# For old Arduino NANO (prior than 2018):
make MODEL=nano:cpu=atmega328old upload
# For Arduino UNO:
make MODEL=uno upload
```
By default, the makefile expects the board to be connected to the
`/dev/ttyUSB0` device. If this is not the case, you can explicitly
specify another device, e.g. `make DEVICE=/dev/ttyS1 MODEL=uno upload`.
ELECTRICAL CONNECTIONS
----------------------
| | |
| --- | ------------- |
| D2 | Encoder 1 (A) |
| D3 | Encoder 1 (B) |
| D4 | Encoder 2 (A) |
| D5 | Encoder 2 (B) |
| D6 | Encoder 3 (A) |
| D7 | Encoder 3 (B) |
| | |
| D9 | Encoder 1 (Z) |
| D10 | Encoder 2 (Z) |
| D11 | Encoder 3 (Z) |
If fewer encoders are needed, do not connect them. This also works with
incremental encoders without the Z index: in this case the counter will
be set to 0 at startup and never reset.
You can skip any encoder, e.g. you are allowed to connect only encoder 2
and 3 without using encoder 1.
To improve reliability, you can put photocouplers between encoder and
arduino, as shown by the above example where only encoder 1 is connected
(see [the schematic](./ardecoder.pdf) for details). In that case,
remember to consider the maximum speed of the photocoupler too.
A [public video](https://www.youtube.com/watch?v=IgxP2A8nXgc) shows
another example on Arduino UNO without photocouplers.
HOW DECODING WORKS
------------------
The code keeps the last state of A B phase (`old`) and compares it to
the new state (`now`). Any variation will increase or decrease the
counter (`raw`) depending on a lookup table (`lut`).
If `OVERFLOW` is defined, it is checked if a phase is skipped (e.g. when
the encoder is turning too quickly) by leveraging another lookup table
(`skp`). If that is the case, the counter is incremented or decremented
by 2, depending on the last adjustment.
```
_______ _______
A ______| |_______| |______
CCW <-- _______ _______ __ --> CW
B __| |_______| |_______|
```
| now
A B | old
A B | lut
| skp
| |
| --- | --- | ---:|:-----:| ---
| 0 0 | 0 0 | 0 | false | No movement
| 0 0 | 0 1 | +1 | false |
| 0 0 | 1 0 | -1 | false |
| 0 0 | 1 1 | 0 | true | One step has been skipped
| 0 1 | 0 0 | -1 | false |
| 0 1 | 0 1 | 0 | false | No movement
| 0 1 | 1 0 | 0 | true | One step has been skipped
| 0 1 | 1 1 | +1 | false |
| 1 0 | 0 0 | +1 | false |
| 1 0 | 0 1 | -2 | true | One step has been skipped
| 1 0 | 1 0 | 0 | false | No movement
| 1 0 | 1 1 | -1 | false |
| 1 1 | 0 0 | +2 | true | One step has been skipped
| 1 1 | 0 1 | -1 | false |
| 1 1 | 1 0 | +1 | false |
| 1 1 | 1 1 | 0 | false | No movement
All 3 counters are adjusted according to the above decoding algorithm by
the PCINT2 interrupt handler, called whenever any of the PIND bits (i.e.
any D0..D7 digital input) changes.
PERFORMANCES
------------
No serious attempts at counting CPU cycles has been performed. I am not
even sure how much the serial communication impacts the overall
performance but I am pretty confident this thing can read more than 20K
steps per second with 3 encoders enabled and `OVERFLOW` disabled.
On real test cases I have seen counting more than 30K steps per seconds
(more than 3K steps in 0.1 seconds, to be exact) but I think I am just
hitting the speed limit of the photocouplers I used.
PROTOCOL
--------
The communication protocol on the USB bus is text based, so it can be
used interactively with a serial console. Requests and responses are
expected to be newline terminated, and any newline format is accepted:
`"\n"`, `"\r"` or `"\r\n"`. Anything between `"#"` and a newline is
considered a comment and it is ignored.
### GET ENCODER DATA
To query an encoder, just send its number (`1`, `2` or `3`) followed by
a newline.
- Example request: `"1\n"`
- Example response: `"1 -581 0 1\r\n"`
The returned fields are respectively:
1. the number of the encoder (`1`, `2` or `3`, the same as the request);
2. the raw counter value;
3. `1` if homed (it passed through the Z phase), `0` otherwise;
4. the number of times a phase was skipped (if `OVERFLOW` is enabled).
### SLAVE OR PUSH MODE
In slave mode (the default), you must manually get the encoder data via
specific queries. For monitoring you must implement by yourself a
polling loop.
In push mode, additionally the encoder data is sent without request
whenever its position changes. The maximum rate of changes (i.e. the
minimum time between two unsolicited responses) is customizable
To enable push mode, use `"S"` followed by the rate time (in
milliseconds) and a newline. To disable push mode and turn back in slave
mode, specify a rate time of 0.
- Request to enable push mode every 0,2 s: `"S200\n"`
- Request to disable push mode: `"S0\n"`
LICENSE
-------
Ardecoder is [MIT licensed](./LICENSE).